P5
Building project in Roosendaal, the Netherlands where low-temperature heating network uses the waste from the Suez waste disposal plant to heat the new homes.
The demand for correct water treatment is therefore rising. Desalination, degassing as well as correcting the pH value of the water in the district heating systems is the key, preferably using significantly fewer and less chemicals. The Danish District Heating Association has published recommendations on water treatment and corrosion prevention, which is one
The use of low temperature also appears in other projects, like waste heat from data centers in Amsterdam, the “Mijnwater” project in Heerlen, and projects with thermal energy from surface water (TEO) or thermal energy from wastewater (TEA). This shows that the Netherlands are not only looking to Denmark as an example, but also beyond, using lower temperature levels and innovative techniques. The low-temperature systems also have new system requirements to pay attention to new pipe materials, different material combinations and new connection types. They can all affect the quality of the water transported by the district energy. We can compare the transported water to the blood in a body; it is important for the health and condition of the system. It is crucial if you expect a system life span of over 50 years. The lowering of system temperatures causes new system conditions. The dissolved amount of oxygen can be more than three times as high in a district heating system at 40 °C compared to a system at 90 °C. In a system with a pressure of 3 bar and 40 °C, up to 18.6 mg/l oxygen can be dissolved in the water, whereas 0.02 mg/l is the limit. This can cause corrosion and thus water leakage, interruption of supply due to maintenance and a shorter life span of pipes etc. In other words, this heavily affects your OPEX. Lower system temperature will also increase bacteriological activity, which can cause biofilm and eventually lead to microbiologically influenced corrosion (MIC) such as pitting or reduction of the heat transfer in heat exchangers, thus reducing the system efficiency.
example of sharing knowledge on how to increase life span and minimize costs at networks and other key assets. EUROWATER has contributed to
the publication and translated the information into English, French and German, making the Danish knowledge available throughout Europe.
There is, however, a need for more knowledge and guidelines on low-temperature systems in relation to water treatment; something that has come to the attention of the Dutch District Heating Foundation “Warmtenetwerk” and needs to be elaborated. The main challenge for the near future lies in the seven million existing houses. For almost two million of them, district heating is seen as a feasible option. At the same time, surplus heat equivalent of nine million houses is thrown away in the Netherlands. This is a future challenge for the Dutch district heating industry.
Christian Broks, cbr.nl@eurowater.com For further information please contact:
www.dbdh.dk
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